An MRAM (Magnetic Random Access Memory) is a nonvolatile memory using a magnetoresistance effect such as TMR (Tunneling Magneto Resistive). The MRAM is attracting attention from the world as a revolutionary next-generation memory having an integrating density equal to that of a DRAM and a high speed equal to that of an SRAM and unlimitedly rewriting data.
As the constitution of the MRAM for example, an underlayer, a multilayer film having a basic structure having a magnetoresistance effect and a cap layer are formed in order on a silicon or glass substrate having a metal wiring line (word line). An antiferromagnetic layer, a magnetization fixed, layer, an insulating layer, and a magnetization free layer are laminated in order from the bottom thereof as examples of the multilayer film.
A magnetoresistance effect element is placed at an intersection point of a word line and a bit line used to read and write a signal, for example. An under layer as a bottom layer and a cap layer as top layer, of the magnetoresistance effect element are respectively processed into a lower electrode and an upper electrode. The lower electrode and the upper electrode are connected to a wiring line. Thereby, the magnetoresistance effect element is used as a memory cell playing a role of an electrode.
Applying electrical current perpendicularly to the upper electrode from the lower electrode in the magnetoresistance effect element freely changes the magnetization direction of the magnetization free layer. Thereby, the height of the electrical resistance value of the electrical current applied in the insulating layer is changed to “0” or “1”. The magnetoresistance effect element exchanges information with the metal wiring line, to perform reading and writing.
An etching technique is generally used to process the magnetoresistance effect element. Examples of the etching technique include an ion beam etching (IBE) method and a reactive ion etching (RIE) method.
Conventionally, the lower electrode and the upper electrode are etched in different steps when the magnetoresistance effect element is processed (for example, see Patent Literature 1).
FIG. 6 represents conventional processing steps for a lower electrode and an upper electrode. FIG. 6A shows a substrate in which a multilayer film 12 and a cap layer 11 serving as an upper electrode are formed on an underlayer 13 formed on a wiring line 14. A state where a protective film 15 and an interlayer film 16 are formed on the substrate so as to cover the cap layer 11, the multilayer film, hp and the underlayer 13 is shown in FIG. 6B. Next, a state where a mask 17 is formed on the interlayer film 16 is shown in FIG. 6C. A state where the lower electrode is formed by transferring a pattern of the mask 11 to the interlayer film 16, the protective film 15, and the underlayer 13 by etching is shown in FIG. 6-D. From this state, a state where the mask 17 is removed is shown in FIG. 6E. Then, a state where the head of the cap layer 11 serving as the upper electrode is exposed by etching the interlayer film 16 and the protective film 15 is shown in FIG. 6F.